1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
|
/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Memory.h>
#include <AK/Singleton.h>
#include <Kernel/Process.h>
#include <Kernel/Random.h>
#include <Kernel/Sections.h>
#include <Kernel/VM/MemoryManager.h>
#include <Kernel/VM/PageDirectory.h>
namespace Kernel {
static AK::Singleton<HashMap<FlatPtr, PageDirectory*>> s_cr3_map;
static HashMap<FlatPtr, PageDirectory*>& cr3_map()
{
VERIFY_INTERRUPTS_DISABLED();
return *s_cr3_map;
}
RefPtr<PageDirectory> PageDirectory::find_by_cr3(FlatPtr cr3)
{
ScopedSpinLock lock(s_mm_lock);
return cr3_map().get(cr3).value_or({});
}
#if ARCH(X86_64)
extern "C" PageDirectoryEntry boot_pml4t[1024];
#endif
extern "C" PageDirectoryEntry* boot_pdpt[4];
extern "C" PageDirectoryEntry boot_pd0[1024];
extern "C" PageDirectoryEntry boot_pd3[1024];
UNMAP_AFTER_INIT PageDirectory::PageDirectory()
{
m_range_allocator.initialize_with_range(VirtualAddress(KERNEL_BASE + KERNEL_PD_OFFSET), KERNEL_PD_END - (KERNEL_BASE + KERNEL_PD_OFFSET));
m_identity_range_allocator.initialize_with_range(VirtualAddress(FlatPtr(0x00000000)), 0x00200000);
}
UNMAP_AFTER_INIT void PageDirectory::allocate_kernel_directory()
{
// Adopt the page tables already set up by boot.S
#if ARCH(X86_64)
PhysicalAddress boot_pml4t_paddr(virtual_to_low_physical((FlatPtr)boot_pml4t));
dmesgln("MM: boot_pml4t @ {}", boot_pml4t_paddr);
m_pml4t = PhysicalPage::create(boot_pml4t_paddr, MayReturnToFreeList::No);
#endif
PhysicalAddress boot_pdpt_paddr(virtual_to_low_physical((FlatPtr)boot_pdpt));
PhysicalAddress boot_pd0_paddr(virtual_to_low_physical((FlatPtr)boot_pd0));
PhysicalAddress boot_pd3_paddr(virtual_to_low_physical((FlatPtr)boot_pd3));
dmesgln("MM: boot_pdpt @ {}", boot_pdpt_paddr);
dmesgln("MM: boot_pd0 @ {}", boot_pd0_paddr);
dmesgln("MM: boot_pd3 @ {}", boot_pd3_paddr);
m_directory_table = PhysicalPage::create(boot_pdpt_paddr, MayReturnToFreeList::No);
m_directory_pages[0] = PhysicalPage::create(boot_pd0_paddr, MayReturnToFreeList::No);
m_directory_pages[3] = PhysicalPage::create(boot_pd3_paddr, MayReturnToFreeList::No);
}
PageDirectory::PageDirectory(const RangeAllocator* parent_range_allocator)
{
constexpr FlatPtr userspace_range_base = 0x00800000;
constexpr FlatPtr userspace_range_ceiling = USER_RANGE_CEILING;
ScopedSpinLock lock(s_mm_lock);
if (parent_range_allocator) {
m_range_allocator.initialize_from_parent(*parent_range_allocator);
} else {
size_t random_offset = (get_fast_random<u8>() % 32 * MiB) & PAGE_MASK;
u32 base = userspace_range_base + random_offset;
m_range_allocator.initialize_with_range(VirtualAddress(base), userspace_range_ceiling - base);
}
// Set up a userspace page directory
#if ARCH(X86_64)
m_pml4t = MM.allocate_user_physical_page();
if (!m_pml4t)
return;
#endif
m_directory_table = MM.allocate_user_physical_page();
if (!m_directory_table)
return;
m_directory_pages[0] = MM.allocate_user_physical_page();
if (!m_directory_pages[0])
return;
m_directory_pages[1] = MM.allocate_user_physical_page();
if (!m_directory_pages[1])
return;
m_directory_pages[2] = MM.allocate_user_physical_page();
if (!m_directory_pages[2])
return;
// Share the top 1 GiB of kernel-only mappings (>=3GiB or >=KERNEL_BASE)
m_directory_pages[3] = MM.kernel_page_directory().m_directory_pages[3];
#if ARCH(X86_64)
{
auto& table = *(PageDirectoryPointerTable*)MM.quickmap_page(*m_pml4t);
table.raw[0] = (FlatPtr)m_directory_table->paddr().as_ptr() | 7;
MM.unquickmap_page();
}
#endif
{
auto& table = *(PageDirectoryPointerTable*)MM.quickmap_page(*m_directory_table);
#if ARCH(I386)
table.raw[0] = (FlatPtr)m_directory_pages[0]->paddr().as_ptr() | 1;
table.raw[1] = (FlatPtr)m_directory_pages[1]->paddr().as_ptr() | 1;
table.raw[2] = (FlatPtr)m_directory_pages[2]->paddr().as_ptr() | 1;
table.raw[3] = (FlatPtr)m_directory_pages[3]->paddr().as_ptr() | 1;
#else
table.raw[0] = (FlatPtr)m_directory_pages[0]->paddr().as_ptr() | 7;
table.raw[1] = (FlatPtr)m_directory_pages[1]->paddr().as_ptr() | 7;
table.raw[2] = (FlatPtr)m_directory_pages[2]->paddr().as_ptr() | 7;
table.raw[3] = (FlatPtr)m_directory_pages[3]->paddr().as_ptr() | 7;
#endif
// 2 ** MAXPHYADDR - 1
// Where MAXPHYADDR = physical_address_bit_width
u64 max_physical_address = (1ULL << Processor::current().physical_address_bit_width()) - 1;
// bit 63 = no execute
// bit 7 = page size
// bit 5 = accessed
// bit 4 = cache disable
// bit 3 = write through
// bit 2 = user/supervisor
// bit 1 = read/write
// bit 0 = present
constexpr u64 pdpte_bit_flags = 0x80000000000000BF;
// This is to notify us of bugs where we're:
// 1. Going over what the processor is capable of.
// 2. Writing into the reserved bits (51:MAXPHYADDR), where doing so throws a GPF
// when writing out the PDPT pointer to CR3.
// The reason we're not checking the page directory's physical address directly is because
// we're checking for sign extension when putting it into a PDPTE. See issue #4584.
VERIFY((table.raw[0] & ~pdpte_bit_flags) <= max_physical_address);
VERIFY((table.raw[1] & ~pdpte_bit_flags) <= max_physical_address);
VERIFY((table.raw[2] & ~pdpte_bit_flags) <= max_physical_address);
VERIFY((table.raw[3] & ~pdpte_bit_flags) <= max_physical_address);
MM.unquickmap_page();
}
// Clone bottom 2 MiB of mappings from kernel_page_directory
PageDirectoryEntry buffer;
auto* kernel_pd = MM.quickmap_pd(MM.kernel_page_directory(), 0);
memcpy(&buffer, kernel_pd, sizeof(PageDirectoryEntry));
auto* new_pd = MM.quickmap_pd(*this, 0);
memcpy(new_pd, &buffer, sizeof(PageDirectoryEntry));
// If we got here, we successfully created it. Set m_space now
m_valid = true;
cr3_map().set(cr3(), this);
}
PageDirectory::~PageDirectory()
{
ScopedSpinLock lock(s_mm_lock);
if (m_space)
cr3_map().remove(cr3());
}
}
|
